The DSP Initiative - Application Notes
Lift Controller for Toshiba, through M. S. Elevator, Malaysia
The aim of this project is to develop an economical lift controller to target markets generated by the construction on Non-high rise buildings with 1-10 floors, where an expensive lift controller from Toshiba Japan, meant for the complex requirements of High-rise buildings, may not be cost-effective.
The Lift Controller will consist of three cards, namely
- Main System Card (MSC) - One per Lift Car
- Hall System Card (HSC) - One per Floor
- On-board Interface Card (OBIC) - One per Lift Car
The architectural representation of the complete system will be as follows -
Main System Card Description
The Main System Card (MSC) will have the following features -
- One Processor (Texas Instruments DSP 320C6712)
- One RS485 port at 1.5 MBPS
- One RS232 port for programming
- One Ethernet port at 10 MBPS
- Interface for multiple lift cars over a backplane bus
- Analog Signal to Drive the AC Drive
- Feedback Input from Drive
- Display for floor number
- Flash for Program Storage
- EEPROM for Parameter Storage
- RAM for Data and Scratch Pad
- Push buttons for Manual Control
- 10 Digital IOs for Manual Control from Lift car
- Power Supply at 24 VDC
The MSC will be the Master Interface for the complete control of the Elevator Car. It will be the one, which will acquire data from the HSC and the OBIC over RS485, and interpret this data and control the elevator car's motion in the shaft based on the protocol for priority and the calls made for the elevator car. It will also be the interface for manual operations either using the push buttons provided on the panel, or using the keyboard provided in the elevator car. It will also be the interface over which data can be sent to a remote location over Ethernet.
Hall System Card Description
The Hall System Card (HSC) will have the following features -
- One Processor (Texas Instruments DSP 320C6712)
- One RS485 port at 1.5 MBPS
- One RS232 port for programming
- Output to Drive the DC Drive for Door Operations
- Two Digital Inputs for UP and DOWN Buttons
- Digital Inputs from Top and Bottom limit switches
- Driver for display of Car Position and Car Approach Indication
- Flash for Program Storage
- RAM for Data and Scratch Pad
- Power Supply at 24 VDC
The HSC will read data from the limit switches and tell the MSC the current position of the car. This will enable the MSC to control the car speed based on the Motion Control Graph below -
The Motion Control Graph depicts the speed curve of the car as it starts moving (Red Color), accelerates attains maximum velocity after which it travels at constant velocity (Green Color) and then decelerates to a stop (Blue Color). In all three phases the acceleration due to gravity must be considered and a PID control to allow velocity to settle must be used. The control is done by the MSC with timely inputs from the HSC and the OBIC. The HSC also provides input to MSC on when and on which floor a call has been made for the car. The MSC then decides in what order to service all the calls made. There will be one HSC on each floor. HSC also controls the display of data above each elevator on every floor, and will give an indication of which floor the car is in, and also which car is going to service the caller.
On-Board Interface Card Description
The On-Board Interface card (OBIC) will have the following features -
- One Processor (Texas Instruments DSP 320C6712)
- One RS485 port at 1.5 MBPS
- One RS232 port for programming
- Analog Signal to Drive the Door Control Drive
- Feedback Input from Door Control Drive
- Flash for Program Storage
- RAM for data and Scratch Pad
- Digital IOs for Lift car buttons
- Power Supply at 24 VDC
- Interface for display on lift
- Audio Interface for Floor and Door status
- Encoder Interface for Elevator Shaft readings
- Interface to Load Cell at the base of the car for overload indication and tripping of motion and for automatic operation of light and fan
- Integration of Smart Card Reader
The OBIC is a board that will be present on each Lift car. It will be responsible for reading the buttons pressed by the user on a lift, and relaying it to the MSC over a high-speed RS485 line. It will also be responsible for reading encoder feedback to check this against settings of the various parameters stored in the EEPROM of the MSC, to ensure that these parameters are updated and correct and also to cross check if the encoder and other limit switches are working fine. The OBIC will also be responsible for acting as an interface to driving the local display and Audio facility on the Lift car based on instructions passed to it by the MSC.
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